The present invention relates generally to an image data coding and/or decoding system which can carry out high-efficient coding of picture signals to transmit and store. More specifically, the invention relates to an image data coding system which can code and transmit picture signals to display an image on a liquid crystal display with a small screen which can be built in a wristwatch and so forth.
In the coding of image data used for a visual telephone (TV phone), a television conference and so forth, the image data efficiently compressed utilizing human""s visual characteristic are used. The human""s visual characteristic with respect to the distortion of a picture utilized here are as follows (see xe2x80x9cImage Information Compressionxe2x80x9d, issued by Japanese Television Society and complied under the supervision of Hiroshi Harashima, page 12).
(1) Frequency Characteristic in Distortion Perception
Distortion varying with elapsed time and distortion with high spatial frequency are difficult to be visible to the naked eye.
(2) Relationship with Pattern of Image
Distortion is easy to be perceived at the flat portion of the image, and difficult to be visible on the contour portion of the image. However, this is the case of a still picture. In a moving picture, the distortion on the contour portion serves as an edge busyness to conversely offend the eye.
(3) Relationship Between Image and Motion
When a picture is moving at a higher speed than a given speed and the user""s eyes can not follow its motion, the perception sensitivity to distortion lowers.
(4) Relationship with switching of Scene
Immediately after a scene has been switched, the distortion is not to be visible to the naked eye if the resolution considerably lowers.
(5) Relationship with Brightness of Screen
The more the screen is dark, the more the picture distortion of the same level is easy to be visible to the naked eye.
(6) Color Signal and Luminance Signal
Since distortion by color signals is more difficult to be visible to the naked eye than that by luminance signals, for example, it is possible to thin out sampled points of the color signals.
In addition, since visual acuity (spatial resolving power) on the peripheral portions of the visual field is worse than that on the central portion thereof under the influence of the distribution of visual receptor cells on retinas, it is necessary for an user to move his eyes (eye movement) in order to obtain information such as shape, structure and detail contents (see xe2x80x9cImage Information Compressionxe2x80x9d issued by Television Society, published by Ohm, page 41). Therefore, to determine the definition of the picture in view of human""s visual characteristic is dominated by the movement of human""s eye serving as a subjective factor in addition to the resolution of the picture serving as an objective factor.
On the other hand, when a human looks at an object, if the object is small, it is possible to recognize the whole shape and so forth of the object by staring a specific range around a point. However, if the object is large, it is necessary to closely observe a wide range including a large number of points to recognize the whole shape and so forth of the object. When he watches a television receiver, if its screen is large, a large number of closely observed points are distributed in a given range by frequently moving his eyes, but if the screen is small, the range wherein the closely observed points are distributed does not so extend.
It is disclosed in xe2x80x9cEstimation Technique of Image Quality and Tone Qualityxe2x80x9d (edited Television Society and published by Shokodo, page 118) that since the display screen in a high quality television system which rapidly approaches to implementation in recent years is greater than those of current television systems, the closely observed points distributing ranges in these systems are different. FIG. 5.22 on the same page of this paper shows the measured results of proportion of the closely observed points distributing range to the area of the screen when observing a high quality television system and a current television system on a standard observation condition using a program of the same content. This figure is expressed by approximating to an ellipse with three times as large as the standard deviation assuming that the closely observed points lie on a normal distribution in horizontal and vertical directions when the center of the screen is the origin. It is also shown the experimental results that the proportion of the distributing range of the closely observed points to the area of the screen is about 60% in the current television systems, but it reaches about 80% in the high quality television system. That is, as the size of the screen decreases, the proportion of the distributing range of the closely observed points decreases and the range concentrates on the center of the screen. Therefore, since the spatial resolving power of the visual sensation on the peripheral portion of the screen is inferior, the information compression can be efficiently carried out by lowering the spatial resolution or by weighting the assignment of the distortion in preprocessing.
By the way, as a method for efficiently compressing the measure of information using the difference between the visual characteristic at the central portion of the visual field (central vision) and the visual characteristic at the peripheral portion of the visual field (peripheral vision), there is a method disclosed in, for example, xe2x80x9cVisual Pattern Image Sequence Codingxe2x80x9d (August 1993, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL.3, NO.4, pp-291-301). In the technique disclosed in this literature, a function relating to the position of radius r from the central point of the screen is derived, and the resolution on the peripheral portion of the screen is lowered using this function.
In addition, as a method for performing the information compression by changing the distribution of the assigned code amount in a visually important region and an unimportant region, there are two methods as follows.
One of the methods has been proposed as applied to a video telephone (Japanese Patent Application Laid-open No. 1-80185 (1989) xe2x80x9cMoving Picture Coding Methodxe2x80x9d). In this method, on the assumption that the closely observed points are concentrated on the face of the opposite party for the telephone conversation, the face region is detected to assign many code amount on the detected face region.
Another method is also applied to a video telephone similar to the aforementioned proposal (Japanese Patent Application Laid-open No. 5-95541 (1993)). Similar to the aforementioned proposal, by detecting the face region to apply a spatial-temporal filtering to a region other than the face, the code amount produced in this region other than the face is decreased, and the code amount assigned in the face region is increased.
Both of these conventional methods pay attention to human""s visual characteristic, and provide a natural picture to a person which visually recognizes a reproduced picture, by changing the coded data amount so that the coding data amount in the region in which the closely observed points are concentrated in the distribution of closely observed points, is different from the coding data amount in the region in which the closely observed points are not so concentrated.
As mentioned above, in both of the conventional image data coding methods, the information compression has been efficiently performed using human""s visual characteristic by restraining the code amount produced in a visually unimportant region and by increasing the code amount assigned to a visually important region. However, both of the techniques disclosed in the aforementioned two publications only classify the regions in the screen on the basis of the degree of concentration of the distribution of closely observed points, to vary the code amount assigned to each of the regions, and these techniques do not consider human""s visual characteristic that the distribution of closely observed points is different by the size (area) of the screen as described in the aforementioned literature xe2x80x9cEstimation Technique of Image Quality and Tone Qualityxe2x80x9d.
In addition, there are problems in that when the image data are transmitted via a radio transmitting channel having a narrower bandwidth than that of a wire transmitting channel, the resolution of the reproduced picture is generally decreased by the limit of the transmitted amount due to the narrow bandwidth, so that the size (area) of the screen is necessarily decreased.
By the way, in conventional image data coding systems, for example, in moving picture data coding systems defined by MPEG, after inputted picture signals are divided into square blocks of 8xc3x978 pixels as shown in FIG. 55, the two-dimensional discrete cosine transform (DCT) is performed for coding.
On the other hand, in xe2x80x9cApplying Mid-level Vision Techniques for Video Data Compression and Manipulationxe2x80x9d (M.I.T. Media Lab. Tech. Report No.263, February 1994), which will be hereinafter referred to as xe2x80x9cLiterature 1xe2x80x9d, J. Y. Wang et.al. disclose that picture signals are divided into a background and a subject (which will be hereinafter referred to as a xe2x80x9ccontentxe2x80x9d) for coding, as shown in FIG. 56. Thus, in order to code the background and the content separately, a map signal called a alpha map indicative of the shape of the content and its position in a screen is prepared. In this coding method, it is possible to vary the picture quality content by content and to reproduce only a specific content. However, as shown in FIG. 55, in a case where the interior of a screen is divided into square blocks for coding, it is required to separately process the blocks containing the boundary portion of the content, i.e. the edge blocks between the inside and outside of the content, as shown in FIG. 57.
It has been also proposed a method for coding picture signals after dividing the interior of a screen into blocks of optional shapes so as to adapt to statistical characteristic in the screen and to the shape of a content. Such a method for performing the orthogonal transform of an optional shape is disclosed in xe2x80x9cExamination of Variable Block Size Transform Coding of Image Using DCTxe2x80x9d (Matsuda et. al., Singaku-Shuki-Daizen D-146, 1992), which will be hereinafter referred to as xe2x80x9cLiterature 2xe2x80x9d. In this specification, this transform method will be hereinafter referred to as xe2x80x9cAS-DCTxe2x80x9d. In AS-DCT, first, one-dimensional DCT is performed in a horizontal (or vertical) direction as shown in FIG. 58(a), and then, after it is rearranged in order of the low of the DCT coefficient as shown in FIG. 58(b), the one-dimensional DCT is performed in a vertical (or horizontal) direction.
Also, in xe2x80x9cEstimation of Performance of Variable Block Shape Transform Coding of Image Using DCTxe2x80x9d (Matsuda et.al., PCSJ92, 7-10, 1992), which will be hereinafter referred to as xe2x80x9cLiterature 3xe2x80x9d, the coding efficiency has been improved by selecting the order of higher coding efficiency as a result of practical coding, as the order of the transform in the horizontal and vertical directions.
Further, xe2x80x9cImage Data-Coding Techniques -DCT and Its International standard-xe2x80x9d written by K. R. Rao and P. Yip and translated by Hiroshi Yasuda and Hiroshi Fujiwara (7.3, pp164-165, Ohm), which will be hereinafter referred to as xe2x80x9cLiterature 4xe2x80x9d, discloses a method for performing the resolution transform of picture signals using the two-dimensional DCT. That is, it is possible to transform the resolution by taking out a part of the DCT coefficient derived by the two-dimensional DCT to inversely transform by the DCT of a different degree, as shown in FIG. 59.
In a picture system such as a graphic display, in order to actualize various image effects, it is desired to perform the resolution transform of a content in a screen for the reduction and enlargement thereof. Since there are contents of various shapes, it is required to perform the resolution transform of contents of optional shapes. However, for example, in the AS-DCT which is a method for performing the orthogonal transform of optional shapes disclosed in the aforementioned Literature 2, it is impossible to actualize the resolution transform in a case where a block to be transformed is an edge block, i.e. a block containing the boundary portion of a content.
In addition, there are problems in that the coding efficiency to an edge block is low in the AS-DCT and other methods for performing the orthogonal transform of optional shapes.
It is therefore an object of the present invention to eliminate the aforementioned problems, and to provide an image data coding system which can efficiently compress information by changing only the assignment of the code amount without changing the absolute amount thereof in accordance with the decreasing of the size of a reproduced picture display, in view of the relationship between the size (area) of the screen and the distributing area of closely observed points.
In order to accomplish the aforementioned and other objects, an image data coding system, according to the present invention, comprises a screen area determining means for determining the size (area) of a screen reproduced on the basis of inputted image data signals, a code amount assigning control means for controlling the assignment of the code amount of data for every region on the screen on the basis of the results of determination, and a coding means for coding the image data signals inputted in accordance with the code amount assigned to every region.
With this construction, the weight function for assigning the code amount corresponding to the size of the screen is set so as to be changed by internally analyzing the inputted image data signals to determine the size of the screen, or by designating the size of the screen in an externally manual set mode. The assigned amount of the code amount is determined using the set weight function, and the coding of the image data signal is performed on the basis of the assigned amount. Therefore, the assignment of the code amount is changed using the weight function in accordance with the area of the screen, so that it is possible to provide the optimum screen for practical use by only determining or designating the size of the screen if the weight function is set in view of human""s visual characteristic.
In an image data coding system, according to the present invention, the screen-area determining means may internally determine the area of the screen of the produced picture on the basis of the amount of the inputted image data signals and so forth, or externally designating the size of the screen in a manual operation. In the case of the determination by internal processing, the amount of the image data signals may be detected to detect the resolution of the produced screen on the basis of the number of pixels of the produced screen. Alternatively, the information relating to the size of the screen, which information are included in a part of the image data signals, may be transmitted to analyze the information by a determining means to determine the size of the screen.
In addition, it is an object of the present invention to provide an image data coding and/or decoding system which can perform the resolution transform of the blocks containing the boundary portion of a content.
It is also an object of the present invention to provide an image data coding and/or decoding system capable of high-efficient coding of the blocks containing the boundary portion of a content.
According to the present invention, the aforementioned and other objects can be accomplished by image data coding and/or decoding systems as described below.
According to a first aspect of the present invention, an image data coding system comprises:
a first coding means for coding a map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
an orthogonal transform means for performing the orthogonal transform of the picture signals in accordance with the map signal to output an orthogonal transform coefficient; and
a second coding means for coding the orthogonal transform coefficient derived by the orthogonal transform means,
wherein the orthogonal transform means performs the two-dimensional orthogonal transform of the picture signals of all the pixels with respect to the blocks located inside of the content, and performs the two-dimensional or one-dimensional orthogonal transform of only the picture signals of the pixels contained in the content with respect to the blocks containing the boundary portion of the content.
For example, with respect to the pixels in the blocks containing the boundary portion of the content, the orthogonal transform means may perform the one-dimensional orthogonal transform in the horizontal or vertical direction after rearranging the pixels contained in the content in the horizontal or vertical direction, and performs the one-dimensional orthogonal transform in the vertical or horizontal direction after putting the derived transform coefficients in order of the lower band of coefficient.
In this case, it may be provided with a correlation detecting means for detecting the respective correlations in the horizontal and vertical directions of the picture signals inside of the content, to switch the direction of the one-dimensional orthogonal transform so as to perform the one-dimensional orthogonal transform in order of the direction that the correlation is higher.
An image data decoding system adapted to the image data coding system, according to the first aspect of the present invention, comprises:
a first decoding means for decoding a coded map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals;
a resolution transform means for performing the resolution transform of the map signal decoded by the first decoding means;
a second decoding means for decoding coded orthogonal transform coefficients;
a coefficient selecting means for selecting an orthogonal transform coefficient necessary to reproduce an image of a predetermined resolution, from the orthogonal transform coefficients decoded by the second decoding means, on the basis of the map signal resolution-transformed by the resolution transform means;
an inverse orthogonal transform means for performing the inverse orthogonal transform of the orthogonal transform coefficient selected by the coefficient selecting means; and
a reproducing means for deriving a regenerative picture signal resolution-transformed from the results of the inverse orthogonal transform by the inverse orthogonal transform means,
wherein the inverse orthogonal transform means performs the two-dimensional orthogonal transform of all the coefficients with respect to the blocks located inside of the content among the orthogonal transform coefficients selected by the coefficient selecting means, and performs the two-dimensional or one-dimensional inverse orthogonal transform of only the coefficients contained in the content with respect to the blocks containing the boundary portion of the content.
For example, with respect to the blocks containing the boundary portion of the content, the inverse orthogonal transform means may perform the one-dimensional inverse orthogonal transform in the horizontal or vertical direction after rearranging the transform coefficients contained in the content in the horizontal or vertical direction, and performs the one-dimensional inverse orthogonal transform in the vertical or horizontal direction after rearranging them to the former positions of pixels.
When the first image data coding system switches the direction of the one-dimensional orthogonal transform so as to perform the one-dimensional orthogonal transform in order of the direction determined that the correlation is higher in the horizontal and vertical directions of the picture signals inside of the content, the first image data decoding system may switch the direction of the one-dimensional inverse orthogonal transform on the basis of the switching information of the first image data coding system.
According to a second aspect of the present invention, an image data coding system comprises:
a first coding means for coding a map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
an average value separating means for outputting an average value of the values of pixels inside of the content, with respect to blocks containing the boundary portion of the content in the picture signals, in accordance with the map signal, and for separating the average value from the values of the pixels inside of the content and for setting the values of pixels outside of the content to be zero for output thereof;
an orthogonal transform means for performing the two-dimensional orthogonal transform of the signals from which the average value has been separated by the average value separating means, to output orthogonal transform coefficients; and
a second coding means for coding the orthogonal transform coefficients outputted by the orthogonal transform means, and the average value.
An image data decoding system adapted to the image data coding system, according to the second aspect of the present invention, comprises:
a first decoding means for decoding a coded map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
a resolution transform means for performing the resolution transform of the map signal decoded by the first decoding means;
a second decoding means for decoding coded orthogonal transform coefficients and an average value of pixels inside of the content;
a coefficient selecting means for selecting an orthogonal transform coefficient necessary to reproduce an image of a predetermined resolution, from the orthogonal transform coefficients decoded by the second decoding means, on the basis of the map signal resolution-transformed by the resolution transform means;
an inverse orthogonal transform means for performing the two-dimensional inverse orthogonal transform of the orthogonal transform coefficient selected by the coefficient selecting means; and
a reproducing means for deriving a resolution-transformed regenerative picture signal by synthesizing the results of the two-dimensional inverse orthogonal transform by the inverse orthogonal transform means, with the average value decoded by the second decoding means, on the basis of the map signal resolution-transformed by the resolution transform means.
According to a third aspect of the present invention, an image data coding system comprises:
a first coding means for coding a map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
an average value inserting means for replacing the values of pixels outside of the content, by an average value of the values of pixels inside of the content in accordance with the map signal, with respect to the blocks containing the boundary portion of the content in the picture signals;
an orthogonal transform means for performing the two-dimensional orthogonal transform of the signals of the average value in the blocks produced by the average value inserting means, to output orthogonal transform coefficients; and
a second coding means for coding the orthogonal transform coefficients outputted by the orthogonal transform means.
In this case, in the average value inserting means, the values of pixels outside of the content may be predicted under the condition that the average value of the pixels outside of the content coincides with the average value of the pixels inside of the content.
An image data decoding system adapted to the image data coding system, according to the third aspect of the present invention, comprises:
a first decoding means for decoding a coded map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals;
a resolution transform means for performing the resolution transform of the map signal decoded by the first decoding means;
a second decoding means for decoding coded orthogonal transform coefficients;
a coefficient selecting means for selecting an orthogonal transform coefficient necessary to reproduce an image of a predetermined resolution, from the orthogonal transform coefficients decoded by the second decoding means, on the basis of the map signal resolution-transformed by the resolution transform means;
an inverse orthogonal transform means for performing the two-dimensional inverse orthogonal transform of the orthogonal transform coefficient selected by the coefficient selecting means; and
a reproducing means for deriving a resolution-transformed regenerative picture signal by taking out the values of pixels inside of the content, with respect to the blocks containing the boundary portion of the content, on the basis of the map signal resolution-transformed by the resolution transform means.
According to a fourth aspect of the present invention, an image data coding system comprises:
a first coding means for coding a map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
a vector quantizing means for performing the matching of the picture signal with code vectors stored in a code book and for outputting an index indicative of a code vector which has the highest correlation to the picture signal; and
a second coding means for coding the index outputted by the vector quantizing means,
wherein the vector quantizing means for performing the matching, with the code vectors, only the signals inside of the content with respect to the blocks containing the boundary portion of the content, in accordance with the map signal.
An image data decoding system adapted to the image data coding system, according to the fourth aspect of the present invention, comprises:
a first decoding means for decoding a coded map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
a resolution transform means for performing the resolution transform of the map signal decoded by the first decoding means;
a second decoding means for decoding a coded index; and
an inverse vector quantizing means, having a code book storing therein code vectors indicated by multiple resolutions, for outputting a code vector designated by the index decoded by the second decoding means,
wherein the inverse vector quantizing means derives a resolution-transformed regenerative picture signal by taking out only the signals inside of the content with respect to the blocks containing the boundary portion of the content, from the code vectors in accordance with the map signal resolution-transformed by the resolution transform means.
According to a fifth aspect of the present invention, an image data coding system comprises:
a first coding means for coding a map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
a subband dividing means for dividing the picture signal into a plurality of subband picture signals;
a resolution transform means for performing the resolution transform of the map signal into the resolution of each of the subband picture signals divided by the subband dividing means; and
a second coding means for coding each of the subband picture signals divided by the subband dividing means,
wherein the second coding means codes only the signals inside of the content with respect to the block containing the boundary portion of the content in the subband picture signals, in accordance with the map signal resolution-transformed by the resolution transform means.
An image data decoding system adapted to the image data coding system, according to the fifth aspect of the present invention, comprises:
a first decoding means for decoding a coded map signal indicative of the position and shape of a content in a screen inputted for every square block of picture signals to be coded;
a resolution transform means for performing the resolution transform of the map signal decoded by the first decoding means, into the resolutions of a plurality of subband picture signals;
a second decoding means for decoding a plurality of coded subband signals; and
a subband synthesizing means for deriving a resolution-transformed regenerative picture signal by synthesizing only the subband picture signals necessary to reproduce an image of a predetermined resolution among the plurality of subband picture signals decoded by the second decoding means,
wherein the second decoding means decodes only the subband picture signals inside of the content with respect to the blocks containing the boundary portion of the content among the subband picture signals, in accordance with the map signal resolution-transformed by the resolution transform means.
In an image data coding and/or decoding system, according to the first aspect of the present invention, it is possible to code transform coefficients and a map signal in a coding system, by performing the two-dimensional orthogonal transform of the picture signals of all the pixels with respect to the blocks (inside blocks) located inside of a content, and of only the picture signals of pixels contained in the content with respect to the blocks (edge blocks) containing the boundary portion of the content, in accordance with a map signal indicative of the position and shape of the content. It is also possible to perform the resolution transform with respect to the edge blocks containing a content of an optional shape in a decoding system, by selecting an orthogonal transform coefficient necessary to reproduce an image of a desired resolution from decoded orthogonal transform coefficients on the basis of a decoded and resolution-transformed map signal, and by performing the two-dimensional orthogonal transform of all the coefficients with respect to the inside blocks and of only the coefficients contained in the content with respect to the edge blocks, respectively.
In this case, it is designed to be able to switch the order of the one-dimensional orthogonal transform in the horizontal and vertical directions in the two-dimensional orthogonal transform, to detect the correlation in the horizontal and vertical directions of the picture signals inside of the content, for performing, first, the one-dimensional orthogonal transform with respect to the direction having higher correlation, so that it is possible to improve the coding efficiency.
In an image data coding and/or decoding system, according to the second aspect of the present invention, in a coding system, by coding a map signal, outputting an average value of the values of pixels inside of a content with respect to blocks containing the boundary portion of the content among picture signals in accordance with the map signal, separating the average value from the values of pixels inside of the content, and setting the values of pixels outside of the content to be zero, to perform the two-dimensional orthogonal transform of the signals from which the average value has been separated, it is possible to code the orthogonal transform coefficients and the average value. In a decoding system, by selecting an orthogonal transform coefficient necessary to reproduce an image of a desired resolution from decoded orthogonal transform coefficients on the basis of a decoded and resolution-transformed map signal, and deriving a resolution-transformed regenerative picture signal by synthesizing the results of the two-dimensional inverse orthogonal transform with the decoded average value of the values of pixels inside of the content, it is possible to perform the resolution transform with respect to the edge blocks containing a content of an optional shape. In addition, it is possible to enhance the coding efficiency in the edge blocks by separating the average value inside of the content from the average value outside thereof for coding.
In an image data coding and/or decoding system, according to the third aspect of the present invention, a coding system can code a map signal, replace the values of pixels outside of a content by the average value of the values of pixels inside of the content with respect to blocks containing the boundary portion of the content among the picture signals in accordance with a map signal, output the replaced values, and perform the two-dimensional orthogonal transform of the signal of the average value in the block to code its orthogonal transform coefficient. In addition, a decoding system can select an orthogonal transform coefficient necessary to reproduce an image of a predetermined resolution from coded orthogonal transform coefficients on the basis of a coded and resolution-transformed map signal, and take out the values of pixels inside of the content with respect to the edge blocks on the basis of the results of the two-dimensional orthogonal transform to derive a resolution-transformed regenerative picture signal, so that it is possible to perform the resolution transform with respect to the edge blocks containing a content of an optional shape.
In an image data coding and/or decoding system, according to the fourth aspect of the present invention, a coding system can code a map signal, perform the matching only the signals inside of a content with a code vector with respect to the edge blocks in accordance with the map signal, perform the vector quantization, and code an index indicative of the code vector of the highest correlation. In addition, in a decoding system, when performing the inverse vector quantization of the code vector designated by the decoded index, only the signals inside of the content are taken out from the code vector with respect to the edge blocks in accordance with a decoded and resolution-transformed map signal, to derive a resolution-transformed regenerative picture signal, so that it is possible to perform the resolution transform with respect to the edge blocks containing a content of an optional shape.
In an image data coding and/or decoding system, according to the fifth aspect of the present invention, when picture signals are divided into subbands to be coded in a coding system, only the signals inside of a content with respect to the edge blocks in subband picture signals are coded in accordance with a map signal resolution-transformed into resolutions of subband picture signals. In addition, in a decoding system, when subband-synthesizing only the subband picture signal necessary to derive a regenerative picture signal of a predetermined resolution, only the signals inside of the content with respect to the edge blocks among the subband picture signals are decoded in accordance with a map signal resolution-transformed into the resolution of each of the subband picture signals, so that it is possible to perform the resolution transform with respect to the edge blocks containing a content of an optional shape.
According to the present invention, a method for performing the two-dimensional orthogonal transform and/or the inverse orthogonal transform for blocks of an optional shape is provided. That is, a two-dimensional orthogonal transform method, according to the present invention, comprises:
a first transform step for performing the one-dimensional orthogonal transform in the horizontal direction in accordance with a map signal indicative of the shape of a block inputted, and for performing the rearrangement in order of the lower of coefficients in the horizontal direction; and
a second transform step for performing the one-dimensional orthogonal transform in the vertical direction in accordance with the map signal, and for performing the rearrangement in order of the lower of coefficients in the vertical direction,
wherein with respect to a signal of an optional shape, the second transform step is performed after performing the first transform step, or the first transform step is performed after performing the second transform step.
According to the present invention, a two-dimensional inverse orthogonal transform method adapted to the aforementioned two-dimensional orthogonal transform method, comprises:
resolution transform step for performing the resolution transform of an input map signal;
a coefficient selecting step for selecting an orthogonal transform coefficient necessary to reproduce an image of the resolution in accordance with a resolution-transformed map signal;
a first inverse transform step for performing the one-dimensional orthogonal transform in the vertical direction with respect to the selected orthogonal transform coefficient, and for performing the rearrangement in the vertical direction; and
a second inverse transform step for performing the one-dimensional orthogonal transform in the horizontal direction with respect to the selected orthogonal transform coefficient, and for performing the rearrangement in the horizontal direction,
wherein a resolution-transformed signal of a block of an optional shape is reproduced by performing the first inverse transform step prior to the second inverse transform step when the first transform step is performed prior to the second transform step, and by performing the second inverse transform step prior to the first inverse transform step when the second transform step is performed prior to the first transform step.